The present invention is directed to a bimetal coil mounting arrangement for a viscous fluid coupling and more specifically to resilient means for damping vibration transmitted to the bimetal coil from the engine to prevent excessive stress of the bimetal coil.
Viscous fluid coupling devices of the type to which the present invention relates are well known in the art and may be better understood by reference to U.S. Pat. Nos. 4,103,765 and 4,185,726.
A typical viscous fluid coupling device includes an output coupling member and a cover member cooperating to define a fluid chamber. The device includes a valve plate disposed to separate the fluid chamber into a reservoir and an operating chamber. An input coupling member is rotatably disposed within the operating chamber and the device includes valve means operable to control the flow of fluid between the reservoir and the operating chamber. The valve means includes a valve shaft extending outwardly through the cover means and being rotatable relative thereto. The rotational position of the valve shaft and the valve is controlled by a temperature responsive bimetal coil element having a first end portion connected to the valve shaft and a second end portion fixed relative to the cover means.
A problem which has arisen in connection with the use of viscous fluid couplings on internal combustion engines relates to the transmission of engine vibrations to the fluid coupling and the bimetal coil element. The excessive application of engine vibrations to the bimetal coil element substantially reduces the endurance of the bimetal coil element.
The viscous fluid coupling devices disclosed in U.S. Pat. Nos. 4,103,765 and 4,185,726 both disclose the use of resilient means for resiliently retaining the outer end of the bimetal coil. While the use of the resilient means reduces the transmission of vibrations from the engine to the bimetal coil to some degree, the primary purpose of the resilient means is to conformingly support the end of the coil to facilitate assembly and to prevent breakage of the coil at the point of securement due to vibration of the bimetal coil.